Previous work by Leamon and Lee has shown the successful targeting of folate labeled polyethylene glycol (PEGylated) liposomes to tumors that express folate receptors. Adaptation of this technology allowed approximately 6000 folate-PEG polymers per microsphere to be covalently linked to the surface of the albumin microspheres. A flow cytometry assay with KB cells, which express high levels of folate receptor, was unable to detect specific targeting of the microspheres under flow cytometry conditions.